[dune] Enable ppx_bisect

The way to run this is:
```
BISECT_ENABLE=yes make -f Makefile.dune test-suite
bisect-ppx-report -I _build/default -html coq-coverage `find . -name 'bisect*.out'
```

Note that support for bisect is still not very optimal
c.f. ocaml/dune#57 , and in particular
support for incremental runs is kinda broken, so running from a clean
tree is recommended for now.

clib/dune

@@ -4,5 +4,6 @@
  (public_name coq.clib)
  (wrapped false)
  (modules_without_implementation cSig)
- (libraries str unix threads))
+ (preprocess (pps bisect_ppx -conditional -no-comment-parsing))
+ (libraries str unix threads bisect_ppx.runtime))
 

engine/dune

@@ -3,4 +3,5 @@
  (synopsis "Coq's Tactic Engine")
  (public_name coq.engine)
  (wrapped false)
+ (preprocess (pps bisect_ppx -conditional -no-comment-parsing))
  (libraries library))

gramlib/dune

@@ -1,4 +1,5 @@
 (library
  (name gramlib)
  (public_name coq.gramlib)
+ (preprocess (pps bisect_ppx -conditional -no-comment-parsing))
  (libraries coq.lib))

interp/dune

@@ -3,4 +3,5 @@
  (synopsis "Coq's Syntactic Interpretation for AST [notations, implicits]")
  (public_name coq.interp)
  (wrapped false)
+ (preprocess (pps bisect_ppx -conditional -no-comment-parsing))
  (libraries pretyping))

kernel/dune

@@ -4,6 +4,7 @@
  (public_name coq.kernel)
  (wrapped false)
  (modules (:standard \ genOpcodeFiles uint63_31 uint63_63))
+ (preprocess (pps bisect_ppx -conditional -no-comment-parsing))
  (libraries lib byterun dynlink))
 
 (executable

lib/dune

@@ -4,4 +4,5 @@
  (public_name coq.lib)
  (wrapped false)
  (modules_without_implementation xml_datatype)
+ (preprocess (pps bisect_ppx -conditional -no-comment-parsing))
  (libraries coq.clib coq.config))

library/dune

@@ -3,6 +3,7 @@
  (synopsis "Coq's Loadable Libraries (vo) Support")
  (public_name coq.library)
  (wrapped false)
+ (preprocess (pps bisect_ppx -conditional -no-comment-parsing))
  (libraries kernel))
 
 (documentation

parsing/dune

@@ -2,6 +2,7 @@
  (name parsing)
  (public_name coq.parsing)
  (wrapped false)
+ (preprocess (pps bisect_ppx -conditional -no-comment-parsing))
  (libraries coq.gramlib interp))
 
 (coq.pp (modules g_prim g_constr))

plugins/ltac/plugin_base.dune

@@ -3,6 +3,7 @@
  (public_name coq.plugins.ltac)
  (synopsis "Coq's LTAC tactic language")
  (modules :standard \ tauto)
+ (preprocess (pps bisect_ppx -conditional -no-comment-parsing))
  (libraries coq.stm))
 
 (library

plugins/ssr/plugin_base.dune

@@ -4,4 +4,5 @@
  (synopsis "Coq's ssreflect plugin")
  (modules_without_implementation ssrast)
  (flags :standard -open Gramlib)
+ (preprocess (pps bisect_ppx -conditional -no-comment-parsing))
  (libraries coq.plugins.ssrmatching))

pretyping/dune

@@ -3,4 +3,5 @@
  (synopsis "Coq's Type Inference Component (Pretyper)")
  (public_name coq.pretyping)
  (wrapped false)
+ (preprocess (pps bisect_ppx -conditional -no-comment-parsing))
  (libraries engine))

printing/dune

@@ -3,4 +3,5 @@
  (synopsis "Coq's Term Pretty Printing Library")
  (public_name coq.printing)
  (wrapped false)
+ (preprocess (pps bisect_ppx -conditional -no-comment-parsing))
  (libraries parsing proofs))

proofs/dune

@@ -3,4 +3,5 @@
  (synopsis "Coq's Higher-level Refinement Proof Engine and Top-level Proof Structure")
  (public_name coq.proofs)
  (wrapped false)
+ (preprocess (pps bisect_ppx -conditional -no-comment-parsing))
  (libraries pretyping))

stm/dune

@@ -3,4 +3,5 @@
  (synopsis "Coq's Document Manager and Proof Checking Scheduler")
  (public_name coq.stm)
  (wrapped false)
+ (preprocess (pps bisect_ppx -conditional -no-comment-parsing))
  (libraries vernac))

tactics/dune

@@ -3,4 +3,5 @@
  (synopsis "Coq's Core Tactics [ML implementation]")
  (public_name coq.tactics)
  (wrapped false)
+ (preprocess (pps bisect_ppx -conditional -no-comment-parsing))
  (libraries printing))

user-contrib/Ltac2/plugin_base.dune

@@ -3,4 +3,5 @@
  (public_name coq.plugins.ltac2)
  (synopsis "Coq's Ltac2 plugin")
  (modules_without_implementation tac2expr tac2qexpr tac2types)
+ (preprocess (pps bisect_ppx -conditional -no-comment-parsing))
  (libraries coq.plugins.ltac))

vernac/dune

@@ -3,6 +3,7 @@
  (synopsis "Coq's Vernacular Language")
  (public_name coq.vernac)
  (wrapped false)
+ (preprocess (pps bisect_ppx -conditional -no-comment-parsing))
  (libraries tactics parsing))
 
 (coq.pp (modules g_proofs g_vernac))